Significant efforts are devoted to developing artificial photosynthetic systems to produce fuels and chemicals in order to cope with the exacerbating energy and environmental crises in the world now. Nonetheless, the large-scale reactions that are the focus of the artificial photosynthesis community, such as water splitting, are thus far not economically viable, owing to the existing, cheaper alternatives to the gaseous hydrogen and oxygen products. As a potential substitute for water oxidation, here, a unique, visible light-driven oxygenation of carboncarbon bonds for the selective transformation of 32 unactivated alcohols, mediated by a vanadium photocatalyst under ambient, atmospheric conditions is presented. Furthermore, since the initial alcohol products remain as substrates, an unprecedented photodriven cascade carboncarbon bond cleavage of macromolecules can be performed. Accordingly, hydroxyl-terminated polymers such as polyethylene glycol, its block co-polymer with polycaprolactone, and even the non-biodegradable polyethylene can be repurposed into fuels and chemical feedstocks, such as formic acid and methyl formate. Thus, a distinctive approach is presented to integrate the benefits of photoredox catalysis into environmental remediation and artificial photosynthesis.

The annual production is still growing and is expected to continue, meaning that it is imperative for us to plan for a future that will have even more plastics.Yet, the ubiquity of plastics has been recognized to be a double-edged sword. It was estimated that 8300 Mt of virgin plastics were produced between 1950 to 2015, but 6300 Mt of them had become plastic waste with 79% accumulated in landfills or the natural environment such as the waterways and the ocean. [1a] In 2015 alone, around 302 Mt or 74% of the annual production had become waste, with only 14% recycled, 14% combusted, and the remainder exposed to the environment (Table 1). [2] Over 8 Mt of plastics are believed to be added to the aquatic ecosystems every year since 2010, [3] with samples being discovered in some of the remotest marine ecosystems like the Mariana trench, including some dating as far back as 1957. [4] The increase in ocean plastics has been especially dramatic since the 1990s. [4a] Besides being potentially toxic by compromising the immune system in different organisms, plastics have also been found to disrupt global biogeochemical cycles such as nitrification and denitrification. [5] Furthermore, the enormous volumes of plastics being produced, converted, and disposed have been estimated to contribute almost 1800 Mt of CO 2 -equivalents (CO 2 e) in greenhouse gas (GHG) emissions in 2015, with the majority (61% or 1085 Mt) generated at the production stage, 30% or 535 Mt during conversion, and the remaining 9% or 161 Mt from the end of life disposal (Table 2). [6] Alarmingly, the current trajectory in growth of plastics consumption suggests that around 6500 Mt of CO 2 e in GHG emissions (15% of the global carbon budget) is expected by 2050. [6] In 2020, owing to the COVID-19 pandemic, even more plastic wastes are being generated due to increases in the use of food and other packaging materials, as well as the proliferation of single use disposal face masks. This has resulted in a surge in criminal recycling scams where plastic wastes from Europe and North America are being illegally exported to Asian countries to artificially inflate the recycling rates in the countries of origin. [7] Patently, more sustainable approaches are needed to manage the entire life cycle of plastics from production to end of life.To manage the inexorable growth of plastics production and waste, one strategy can be to adopt a zero waste hierarchy that was proposed by the European Commission's Waste Plastics are now indispensable in daily lives. However, the pollution from plastics is also increasingly becoming a serious environmental issue. Recent years have seen more sustainable approaches and technologies, commonly known as upcycling, to transform plastics into value-added materials and chemical feedstocks. In this review, the latest research on upcycling is presented, with a greater focus on the use of renewable energy as well as the more selective methods to repurpose synthetic polymers. First, thermal upcycling approaches are briefly introduced, inc...

Visible light assisted photocatalytic organic reactions have recently received intense attention as a versatile approach to achieve selective chemical transformations, including C-C and several C-X (X = N, O, S) bond formations under mild reaction conditions. The light harvesters in previous reports predominantly comprise ruthenium or iridium photosensitizers. In contrast, selective, photocatalytic aliphatic C-C bond cleavage reactions are scarce. The present study focuses on rationally designing V V oxo complexes as molecular, photoredox catalysts towards the selective activation and cleavage of a C-C bond adjacent to the alcohol group in aliphatic alcoholic substrates. We have employed kinetics measurements and DFT calculations to develop a candidate for the catalytic C-C bond activation reaction that is up to 7 times faster than our original vanadium complex. We have also identified a substrate where the C-C bond cleaves at rates 2.5-17 times faster, depending on the catalyst used. In order to better understand the effects of ligand modification on the thermodynamics and catalysis, DFT calculations were employed to reveal the orbital energies, the electronic transitions during the C-C bond cleavage, and the activation barriers. Our combined kinetics and computational studies indicate that the incorporation of electron withdrawing groups at select sites of the ligand are essential for the development of active and stable vanadium photocatalysts for our C-C bond cleavage reactions.

Our society's current energy demands are largely met by the exploitation of fossil fuels, which are unsustainable and environmentally harmful resources. However, Nature has provided us with a clean and virtually limitless alternative in the form of solar energy. This abundant resource is utilized constantly by photosynthetic organisms, which has in turn motivated decades of research in our quest to create artificial counterparts of comparable scales. In this feature article, we will highlight some of the recent novel approaches in the field of artificial photosynthesis (AP), which we define by a more general term as a process that stores energy overall by generating fuels and chemicals using light. We will particularly emphasize on the potential of a highly modular plug-and-play concept that we hope will persuade the community to explore a more inclusive variety of multielectron redox catalysis to complement the proton reduction and water oxidation half-reactions in traditional solar water splitting systems. We discuss some of the latest developments in the vital functions of light harvesting, charge separation, and multielectron reductive and oxidative catalysis, as well as their optimization, to achieve the ultimate goal of storing sunlight in chemical bonds. Specific attention is dedicated to the use of earth-abundant elements and molecular catalysts that offer greater product selectivity and more intricate control over the reactivity than heterogeneous systems. In this context, we showcase our team's contributions in presenting a unique oxidative carbon-carbon bond cleavage reaction in aliphatic alcohols and biomass model compounds, under ambient atmospheric conditions, facilitated by vanadium photocatalysts. We offer this discovery as a promising alternative to water oxidation in an integrated AP system, which would concurrently generate both solar fuels and valuable solar chemicals.

Being a handle for synthesizing quaternary carbon centers and olefins, together with ubiquitous appearance in organic building blocks makes tertiary alcohols valuable targets in synthesis. However, traditional syntheses of these alcohols have faced several challenges including the employment of functionalized reactive reagents, undesirable side reactions and decomposition of the alcohol products under harsh conditions. The paucity of synthetic approach to bulky tertiary alcohols prompts our interest to develop a benign catalytic protocol to tackle the current issues. Here, we have successfully demonstrated the use of ketyl radicals in intermolecular cross radical-radical coupling, which has opened the new door for accessing complex tertiary alcohols. On the other hand, by starting from feedstock and naturally derived chemicals without any preactivation, it would be superior to traditional methodologies in industrial context.

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